Linux 3.16 LTS Kernel for Odroid C2

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Re: Linux 3.16 LTS Kernel for Odroid C2

Unread postby tobetter » Thu Jun 07, 2018 10:42 pm

sebas wrote:Wouldn't the device tree entry + driver be just ignored if related device wasn't available?

On 3.14, the rtc driver was not part of kernel as it shared pin use with GPIO driver, which makes them exclusive. Since here it's already in the kernel, that reason is no longer applicable.

So if above (about ignoring) is true, could be included?

The device tree can enable the RTC driver by default and the driver won't be active when RTC component is not connected. Beside kernel boot would be slow since RTC device driver will encounter the timeout on an I2C bus due to missing RTC component.
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Re: Linux 3.16 LTS Kernel for Odroid C2

Unread postby crashoverride » Fri Jun 08, 2018 2:48 am

sebas wrote:Wouldn't the device tree entry + driver be just ignored if related device wasn't available?

No, the driver would send out I2C data probing for the device. This could potentially conflict with another I2C device or cause boot delays.

sebas wrote:Since here it's already in the kernel, that reason is no longer applicable.

The RTC driver should be included in the kernel whether its used or not. The reason is that its available before any filesystems are mounted. If it is a module, the correct time will not be known until after a filesystem is mounted and the driver can be loaded. This behavior can affect certain use cases.

Traditionally, non-standard hardware is not included in device tree or the kernel.
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Re: Linux 3.16 LTS Kernel for Odroid C2

Unread postby moon.linux » Fri Jun 08, 2018 3:28 am

RTC module should have been continued from the C1+ to C2 series.
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Re: Linux 3.16 LTS Kernel for Odroid C2

Unread postby sebas » Sun Jun 10, 2018 2:50 am

Thx for the clarifications.
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